Investigating an Invalid Inventory

Today, as my technician was dispensing material for the 18-month interval for a study, she noted that after pulling the sample only 6 bottles remained, while the LIMS inventory indicates 9 bottles should be on hand after today’s pull. The technician confirmed with her colleagues that no one else had pulled samples earlier. She also confirmed that no previous extra or non-routine pulls were documented in the system - those would have deducted from the inventory anyway.

There’s just 6 more months left for this stability study (24-month expiry) supporting a solid oral dosage antibiotic in 90-count bottles. The study was initiated to support a manufacturing excursion event from 2021, but since it was a minor excursion QA decided to simultaneously use the study to support the annual requirement (cost savings). At the time, the plant could only give us enough extra material to cover 2 additional intervals - 6 extra bottles. Somehow, it looks like we now only have 3 extra.

Our program involves about 190 studies supporting 12 different product lines - all solid oral dosages. We perform annual 100% inventory checks and last year, in March 2022, no errors were found, but that was before the 12-month interval for this study in June 2022. So, probably somewhere in the last 10 months 3 bottles of product have gone missing, which would cast some doubt on our chain of custody and sample integrity systems. I will initiate a formal investigation into this discrepancy.

The first thing I would suggest is to check other storage locations to confirm they were not simply misplaced. I’m not even sure if that would warrant a formal investigation if that’s all it was. In fact, your upcoming annual inventory (assuming it will be in March, again) would have caught and corrected this discrepancy if the technician hadn’t caught it while dispensing. What are some tricks of the trade you have used to help pinpoint sources of an inventory error?